Integrated circuitry fabrication typically involves lithographic processing to transfer patterns formed in an imaging layer to an underlying substrate material which will form part of the finished circuitry. One example process is photolithography wherein the imaging layer comprises a photoresist material. The photoresist material is typically formed over a layer to be patterned either by ion implantation, etching or other processing. The photoresist is then masked or otherwise processed such that selected regions of the photoresist are exposed to actinic radiation and thereby patterned. The photoresist is then processed in a manner which removes either the processed or unprocessed portions of the photoresist such that openings extend therethrough to the underlying layer to be patterned.
One process of doing so is by exposure of the photoresist through a mask or reticle to actinic energy to modify the solubility of the exposed region relative to a suitable solvent. The imaging layer is then typically solvent processed to remove one or the other of the processed or non-processed regions, thereby forming the photoresist layer to have mask openings extending entirely therethrough to the underlying layer to be patterned. Typically, the substrate is then subjected to a suitable etching chemistry which is selected to etch the underlying layer or layers and little if any of the photoresist, thereby transferring the imaging pattern to the underlying circuitry layer or layers. Alternately, other processing might be conducted through the patterned openings (i.e., ion implantation) to otherwise form a suitable desired pattern in the underlying layer or layers.
The photoresists utilized are typically entirely transmissive of the actinic energy utilized for their exposure. Unfortunately, some underlying layers are highly reflective of the incident actinic energy, thereby reflecting a substantial quanta back into the photoresist. This can adversely affect resolution and depth of focus, resulting in a less than desired transfer of the mask or reticle pattern into the photoresist.
One known method of reducing such reflection is to provide an antireflective coating over the layer to be patterned prior to the deposition of a photoresist layer thereover. The exposure to actinic energy is thereby intended to be absorbed by the antireflective coating as opposed to reflected back into the photoresist layer. After the exposing to actinic energy, the photoresist is then typically wet processed to form the openings therethrough to the antireflective coating. Thereafter, a different and dry chemistry processing is typically utilized to extend the openings from the photoresist through the antireflective coating to the ultimately desired layer therebeneath to be patterned.
One common antireflective coating material includes an inorganic silicon oxynitride layer. Organic antireflective coatings are also known in the art.